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Wednesday, June 25, 2008 09:59 am

Knocked out by Knock Out Roses

New breed has changed the way gardeners use these flowers

Untitled Document One of my favorite flowers is the rose. Roses are beautiful, but they require a great deal of time and maintenance. Growers must spray for diseases and insects, prune, water, fertilize, and provide protection during the winter. For this reason, the only rose I have in my landscaping is the Knock Out rose, a carefree variety that fits my low-maintenance style of gardening. William Radler, of Milwaukee, Wis., is the breeder of the Knock Out rose family. Radler, who began growing roses when he was 9 years old, wondered whether roses could be bred that would be beautiful as well as resistant to pests and disease. His lifelong pursuit was to “breed a rose that everyone can grow and enjoy.”
By 1988, after 15 years of trial and error, Radler had developed what would become the Knock Out rose; it would be introduced to the public in 2000. (To read more of Radler’s story, go to www.theknockoutrose.com/breeder.cfm.) All-America Rose Selections hailed the Knock Out as a breakthrough shrub rose because of its exceptional disease resistance and hardiness — it’s resistant to blackspot and rose midge and tolerant of powdery mildew, and some are resistant to rust. It is also self-cleaning, has a nice purple fall leaf color, and thrives in the heat and humidity of summer. The Knock Out doesn’t need much winter protection: It’s crown hardy to minus-20 Fahrenheit. Knock Out roses are hardy in zones 4 to 9. They perform the best with full sun exposure and continuous moisture. The Knock Out rose has changed the way in which gardeners use roses. The shrub rose, originally released in a cherry red, is now also available, in single and double blossoms, in pink, hot pink, yellow, and a pink-and-yellow combination. Knock Out roses bloom continuously from spring to frost; most grow 4 feet tall and 3 feet wide. Here are the members of the Knock Out family: • Rosa Radrazz, the original introduction, has single cherry-red blooms. It was the All-America Rose Selection award winner in 2000. • Rosa hybrida Radtko has double cherry-red blossoms. • Rosa Radcon has single to semidouble pink flowers. • Rosa Radtkopink has a hot-pink bloom. • Rosa Radyod has a light-pink bloom that changes to shell pink as it ages. • Rosa Radcor, a 2007 introduction, has a coral-pink bloom painted with rich yellow at the base. This variety — more compact and floriferous than the original introduction — was an All-America Rose Selection award winner in 2007. • Rosa Radsunny is a new release. Blooms open as a bright yellow and turn a creamy white when fully open. It seems that the only drawbacks to the Knock Out rose are that (a) the flowers have only a faint fragrance or none at all and (b) everyone seems to have one. For more information on growing roses, go to the University of Illinois Extension’s Web page “Our Rose Garden,” www.urbanext.uiuc.edu/roses.
Jennifer Fishburn is a horticulture educator with the University of Illinois Extension Sangamon-Menard Unit. Contact her at fishburn@uiuc.edu.
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